what I've seen...
An older retired friend of mine used that "Gauranteed to Pass" stuff in his Ford motor home, with a carbed 460--he failed the first attempt,so he buys that stuff,and dumps it in the tank--we go for a 20 mile cruise down the highway--with each mile, the RV ran better and better!---
---it had sat almost a year without being started..the "rich" smell from the exhaust dissapeared,and when we went back to the inspection station,it passed with flying colors!..even the guy doing the inspection was shocked when we said all we did was add that stuff,and didn't do a tune up,or monkey with the timing,etc..I was impressed,I had little faith it would help any..
I've used 2 or 3 bottles of isopropanpl "dry gas" to a 1/4 tank of gas,to do much the same thing..it leans out the mixture enough to "fool" the sniffer into thinking its running clean..I haven't failed an emission test yet by doing this..
If your rings are passing oil,the "Smoke Stop" or similar stuff like STP will help--it wont do squat for the "chevy puff" syndrome--only new valve stem seals and or guides will correct that..but every Chevy SB I've had has the "chevy puff",and they all pass emissions easily...and they all never have a "dry" start!--at least in the cylinders the seals are leaking into!..
I'm sweating the sticker on my 82 K20--it expired in January!--and now I hear MA is doing "random" emission tests on diesels!!!--I hope its "exempt" from that because its an 82!..."random" probably means ALL older ones!!
Oh BTW--you guys in MA,dont run around with an expired sticker or a "reject" sticker...they recently raised the fines for not having a current sticker--its now 75 bucks instead of 50!--and for each month it was past expiration,they add on 50 bucks more PER MONTH!...

..plus it can go against your insurance,and you could get surcharged!!..

...its far cheaper to get a sticker!...
